PRACTICAL CONSIDERATIONS: THE AORTIC ARCH. 727 



the thorax. In persons with small chests the upper border may almost reach the 

 level of the top of the manubrium, while in those with large chests it may be no 

 higher than the junction of the first and second pieces of the sternum {angulus 

 Ludovici) . The transverse portion reaches the left side of the vertebral column at 

 a level just above the fourth thoracic spine. The third (descending) portion and 

 the thoracic aorta lie at first a little to the left of the body of the fourth thoracic 

 vertebra and gradually incline to the mid-line, passing through the diaphragm at the 

 level of the twelfth thoracic vertebra. 



Aneurisms of the aorta are more frequent than are those of any other vessel, on 

 account of the great strains to which the aorta is subject. They may most con- 

 veniently be considered here by following the anatomical subdivisions of the vessel, 

 premising, however, that the symptoms thus described frequently commingle and 

 overlap. 



A. The ascending portion is more subject to aneurism than are the remaining 

 portions, because it receives the first and most vigorous impulse of the heart's stroke, 

 and because it is within — enclosed by — the pericardium, and its walls are not rein- 

 forced by blending with the fibrous pericardial layer, as is the case in the second 

 and third portions. Aneurism most frequently involves the region of the anterior 

 sinus of Valsalva, where regurgitation of blood chiefly takes place ; or, if higher, the 

 anterior wall of the aorta in the vicinity of the normal dilatation, probably due to the 

 impact of the blood-current leaving the heart. The symptoms are : i. Venous co?i- 

 gestion, causing (^a) lividity of the face from pressure on the descending cava, the 

 left innominate, and the internal jugular veins ; i^b) dizziness and headache from the 

 same cause ; (^) sivelling and oedema of the right arm from pressure on the sub- 

 clavian vein ; (^d\ swelling and oedema of the ajiterior thoracic wall from pressure on the 

 internal mammary, azygos, or hemiazygos veins. 2. Dyspnoea with altered breath 

 sounds over the right chest, from pressure on the root of the right lung. 3. Dys- 

 phonia or aphonia, with croupy or stridulous respiration, from pressure on the right 

 recurrent laryngeal nerve ; sometimes from venous congestion due to pressure on 

 the internal jugular and innominate acting through the superior thyroid and inferior 

 thyroid veins on the corresponding laryngeal veins. 4. Sivelling or tumor, often 

 first seen at or about the sternal end of the third right intercostal space. 5. Dis- 

 placement of the heart, occasionally occurring when the aneurism involves especially 

 the concave side of the vessel and pushes the heart downward and to the left. 6. 

 Ascites and oedema of the legs and feet from compression of the ascending cava when 

 the aneurism occupies the same situation. 7. Pain in the sternum, the ribs, or the 

 spine from direct pressure ; encircling the upper part of the chest from pressure on 

 the intercostal nerves ; running down the side of the thorax and the inner surface of 

 the arm from pressure on fibres distributed, by the intercosto-humeral nerve. 



B. Aneurism of the transverse portion may cause : i. Dyspnoea and dysphonia 

 or aphonia from direct pressure on the trachea or bronchi, or from involvement of 

 the left recurrent laryngeal nerve in its course around the arch. 2. Dilatation of 

 the pupil foUovved by contraction from, first, irritation and then paralysis of .the 

 sympathetic. 3. Inanition from pressure on the thoracic duct. 4. Swelling, begin- 

 ning in the mid-line, then extending to the right (only four left-sided cases out of 

 thirty-five aneurisms, Browne, quoted by Osier), and sometimes simulating innomi- 

 nate or cQjpimon carotid aneurism. 5. Venous co7igestion of the head, neck, left arm, 

 etc. , often more marked on the left side from the greater exposure to pressure of the 

 left innominate vein. 6. Weakness or absence of radial or temporal pulse — espe- 

 cially on the left side — due to pressure on or involvement of the innominate, left sub- 

 clavian, or left carotid artery. 



C. Aneurism of the descending portion of the arch and of the thoracic aorta 

 may cause : i. Dysphagia, which is common and apt to appear earlier on account 

 of the more direct relation with the oesophagus. 2. Great pain m the spine, some- 

 times followed by paralysis, from erosion of the vertebrae and compression of the 

 cord. 3. Swelling in the left scapular region or at the vertebral ends of the middle 

 ribs on the left side. 4. Bronchiectasis, with cough and expectoration, from press- 

 ure on the left bronchus, or asthmatic attacks from involvement of the left pulmo- 

 nary plexus. 



